Detection of the chemical condition of materials



c. F. WALLACE 2,396,934 DETECTIAON OF THE CHEMICAL CONDITION OF MATERIALS 3 sheds-sheet `1 Filed Aug. 3, 1940 Illu/l mail@ IMM@ ATTOREY March 19, 1946. c. F` WALLACE 2,396,934

DETECTION OF THE CHEMICAL CONDITION 0F MATERIALS Filed Aug. s, i940 3 Sheets-Sheet 2 www@ SS mw Rum ATTORNEYS Mach 19, 1946. c. F. WALLACE DETECTION OF THE CHEMICAL CONDITION OF MATERIALS Filed Aug. 3, 1940 5 Sheets-Sheet 3 ATTORNEYS Patented Mar. 19, .1.946 i uNi'rEDifQsiiiri:'sf

#PATENT can@ N. J., a -corpration-offhlew .I ers'eyA A I Application August 3,- 1940, Serial No. 350,712

'L19 claims."

chemical condition'of materials, andl more particularlyto procedure and apparatus' `for deter'- mining the presence and quantity of a .substance lor other chemical characteristic in a flowing liq- .uid or a large body of liquid; an example of such determination being for the measurement of the amount of a given substance introducedvby or re-. jmaining Afrom aparticular treatment of the liquid. Thus, an important embodiment of` the /in' 10 vention is in detecting the chlorine concentration in water, sewage, or other liquids, which may have been treated withv chlorine.

I Certain principal objectsofl the invention are to 'provide improved. procedure. and apparatus *of` the character stated, wherein theliquid ndergoing test need onlybe sampled-at one point;-

wherein the eiect of other chemicals or matef rials in the liquid may be balanced out to restrict the reading substantially to the effect alone of the substance under measurement; wherein the indications or measurements may have a substantially linear relationship to the concentration of the given substance, e.g., chlorine, in the sampled liquid; land wherein the detection of the sub- 25 stance, such as chlorine, may be edected t oughl electrolytic instrumentalities in such a way, i de.- sired, that relatively littleor nocurrent is drawn except at times ofextreme unbalance. r

Further objects include the provision of methods and means toaord more accurate, eilicient and economical operation inthe detection, indication or recording loi? the concentration of a sub stance ina uid, or for operating control instru mentalities' in laccordance with such -concentration; additional objects including such as are hereinafter stated or as will be apparent from the following description and appended drawings.

l To these and other ends, importantfeatures of the invention for the determination of 'a given substance say chlorine in water, -sewage or other liquid, may include sampling the liquid at--a pref- 'erably constant rate, dividing the sampling into -two portions. subjecting one o f the portions, to a treatment adapted to neutralize or remove the substance,`.thereafter lsubjecting the fso treated portiont to fresh application oi the substance 'at a knownor detectable rate, and then conducting both ortions of the sam lin to. a ratus for p p g ppa 50 change in the composition of a liquid. Accordcomparing their respective concentrations yof the substance. Although thereare various ways for eiiecting such comparison` for example, in the c ase of chlorine, by adding ortho-tolidin solution to the treated and untreated samples and photoelectrically detecting the color which is rep-L n l t www-es) This'invention relates to the detectlonof-.the j resentative of'chlorinevcontent in each portion);

particularly. eiiicient' results are obtainable with vchemically sensitive electrolytic cells. Further-V provisions are preferably included wherebythe comparing step, carried out with electrolytic 'cell apparatus or; other suitable indicator, is automatically caused'to control the rate' of.-substance addition to that portion which ,has beensubjeted to the treatment for removal of substance. Thus upon adjustment, for example, of the ratev of substance addition to a point of balance,l where the comparison step yields a -nuli'result (i. e., an. indication that the. treated andv untreated portions are alike), such rateo! 1.5 substance yaddition to the. mst-mentioned porl ition of `the sampling may be read, recorded lor otherwise utilized to aiord an accurate repre.-

sentation of substance concentration in the original liquid. In this Way the desireddetermination 20 is obtained independently orsubstantially inde- K 4pendently of the content of other materials in the liquid, and also independently or non-linear or other undesirable `characteristics of the substance-sensitive indicator, aswell las without, del eterious current'drain from the indicator (as where thelatter isan electrolytic celllof a type that is aiected by current drain); -and at the same time, the advantages of testing by comparison are fully realized with a sampling oi' the '30 liquid at only a single point.

By way of example, certain presently preferred embodiments of the invention are hereinafter described andillustrated in the drawings, wherein: Fig. 1 is aview, chiefly diagrammatic, oi: one

35 system embodying the invention;

, Fig. 2 is a similar View of a somewhat modiled embodiment;

Fig. 3 is a view, partly in vertical section and partly diagrammatic, of a chemical feeding de- 40 vice. adapted to be used or substituted in the apparatus of Figs.r 1 and 2?; i

FigA illustrates .a modified form of theapparatus shown inF-ig.3; and 1 Fig. 5 is a'detail view illustrating a modificaon of a part' of the apparatus of Fig. 4.

While the invention is'susceptible `ot use in!l other combinations and environments, it is very advantageously adapted for` systems to detect ingly, thel systems shown in the ydrawings will 2 a system involving treatment by the application of chlorine or chlorine-liberating material,

into two.'portions, one of which flows through a `further conduit 3 to a constant level chamber l,

from 'which it is fed to one side of an indicating or comparing device comprising, for example, the chlorine sensitive cell 5. Theliquid thus flows into, the cell through the restricted section l of the chamber I 'and thereby impinges 4directly against one electrode I of the cell. The chamber August 18, 1939, the latter of which is now Patent No. 2,350,378, issued June 6, 1944, may be em 4 includes an overflow outlet l whereby' a constant head or pressure is maintained'atY theoutlet orifice 9 of the restricted section l, so as to introduce the liquid at a constant pressure and rate. An overflow pipe 4Il in thecell exhausts the liquid to waste` therefrom. and maintains a predetermined level. A` valve il is conveniently 4`provided in the conduit 3 for appropriate adjustment to prevent an excessive amount of liquid being run to waste through the overflow pipe I.

The other portion of the sampled liquid in the pipe 2 is conducted through a valve Ila, similar in function and Purpose to the valve Il, to a dechlorinating device generally designated i2. Althoughother apparatus may be employed for treatment of the sampled portion to remove therefrom the substance in question, e. g. chlorine, the de-chlorinator i2 is shown, for lil-1190565 of illustration, as a device which is available on the market and known as the Hydrodarco Purifierand which is manufactured by the International Filter Company of Chicago.,Illinois. .The form of such unit which is at present preferred comprises a layer oi graded sand I3, a layer of activated carbon I4, and a further layer of graded sand l5, through which the liquid successively passes. By "graded sand, I mean that the upper portion oi' each of the sand filter sections I3 and i5 is composed of relatively ne sand particles, the intermediate portion of coax-ser par-` ticles and the bottom portion of still coarselparticles or ne gravel.

In this filter device l2 the activated carbon eiectively removes all traces of chlorine from the water, which then exhausts into a constant level box i6 where it is Amaintained at a desired head by means of the overow tube Il. From the box IB the liquid iiows at a, constant pressure and rate through a tube I8 to apparatus for the introduction of chlorine-here shown, for exam- 4ployed, and although a detection circuit might thus,.for example, be utilized in which the effect depends on depolarization produced by the presence of chlorine and affords a ilow y of current at. all times, I have shown,'for purposes of illustration', a cell of a type illustrated in` mycopending Patent No. 2,289,610, issued July 14, 1942 (wherein certainnovel features 'and combinations in such electrolytic' cell apparatus areclaimed) As is more fullydisclosed in4 my Patent No. 2,289,610, the ycell 5 may linclude two liquid electrodes l, 24e. g. of mercury, which have their surfaces agitated and maintained in a clean and accurately potential-responsive condition by the impingement of the jets of water fromthe orices 8 and 23 respectiveljn The cellis divided into two portions by a permeable or porous partition 24a, -and 'as will' now be understood, it is adapted to provides. difference of potential between the electrodes 24 and 'l upon a difference in chlorine concentration ofthe' liquids in the corresponding cellportions. i t

The illustrated aspirator device i9 comprises a receptacle for a body of liquid which is fed below ,its surface bythe pipe I8, the outlet from the receptacle being afforded by the tube 20 opening upwardly therein as shown so that as the liquid flows overand down through the top of the tube it entraps and carries away such air or gas as may be delivered through a feed conduit a extending up from the top of the device. That is to say, in eifect, the aspirator produces a small amount Ofyacuum or-suction in the line 25a so as to draw into and mix ywith the liquid,

the gas (inthis instance, chlorine) which it is de-` sired to add.

Although other chlorine generatorapparatus may befemployed, I Have conveniently illustrated' a generating cell 26 ofthe general type described in my Patent No. 1,678,625 issued July 24, 1928, iorApparatus for the therapeutic application of chlorine. While a more completedescriptionv of the device may be had by reference to the cited patent, a brief explanation o f lit is here set forth. A container 21 whichmay be of glass or other suitable material is arranged to hold a small quantity of an appropriate electrolyte such as 'hydrochloric acid.' Within the jar 2l is inserted a tubular porous diaphragm 28 inert to the action of chlorine, which has supported -on its outer surple, as including a special form of aspirator i8- and thence through a further tube 20 into a feed Chamber 2|,- having a restricted portion 22 and outletoriflce 23 like elements Ii and 9 of chamber '4, for impingement upon another electrode 2l of the cell 5. As stated, the box I 6 provides a constantl pressure and velocity of the liquid at the It will be understood that various forms of cells or other concentration sensitive indicators may be utilized to provide' the detectionk and comparison allorded by the apparatus designated `5 in this ligure. Thus, although cells of the type disclosed in Patent No. -1,944,803to Georg Ornstein. or

face an electrode 29 that may be made from a spirally wound silver wire.' Inside the tube 28 there is disposed a suitable electrode 30, for example of platinum or a', graphite rod, from the surface of which chlorine gas is liberated when electric current flows through the cell and its associated circuit. f fr i A hard rubber block 3i is recessed to contain one end of the electrode 30 and of the porous tube 28 and to mount the positive and negative terminal posts which connect to their respective electrodes.

"s 3l for entrance of the tube 25a and the block also cells ofthe type disclosed in my copending patent applications, Serial Nos. 290,841 and 290,842,1iled 1 For operation of the cell 28, alternatingl current has a duct 32 which permits communication between the interior of the tube 28`and the atmos.-

phere. As'fully explained in my cited U. S. Patent No. 1,678,625, the passage of electric current through the cell 26 causes the production of chlorine gas at the positive electrode 3|?. The amount of gas produced depends upon the current nowing through the cell and vbears a substantially uniform and linear relationship to the same.

A passage isr provided in 'the block' `contact arm 39 of the relay .91,996,934]` "--is supplied from a transformer 3 3 to a rectifier i 3l, convenientlyof the full waveJdrydisc type,

which is thus adapted to produceat its output terminals a" substantially continuous direct current.` As shown, the output terminals of the recti-` l" iierare connecte in series with the cell, farecording instrument 5, anda variable resistance or i -slide wirefai. Although other types of indicating or recording instruments maybe employed, preferably an 'instrument adapted to affordY a sub- 'stantiallyr linear response tp variations of current flow, it is presently preferred toemploy a. recording meter'oFthe galvanometer type disclosed vin myPatent No. 2,350,"L8, citedhereinabove; such instruments being sensitive, emcient and especially ,adapted for measurements o f the character here contemplated. It will now be appreciated that the current through the cell 26 'andvhencelits rate of chlorine evolution, may be'readily controlled by adjustment of the slide 3wire 36,v say fromm position for a predetermined low or. even zero current, tofa. convenient maximumcurrent 4i. e., low resistance) position.` For nometer type relay I3T has its movable coil 38. con'- nected to the electrodes 1 and 24. .The beam or l is. adapted. for deectioxrto the left or right, depending upon the control by the cell 5, a .sensitive galva- I assumed to 'be closed),

3 wound. "shading coils l1 'cf-theseryoJmotor l2. flikewise. as' disclosed in the cited. patent'and British-patent. The field winding 48 `of the mov tor 'isconnected for energization from the A. C. line preferably throughthe contacts' 50 ofan intermediate camming device -hereinafter described. It willl now be understood that the arrangement oi`\the two pairs of shading coils1 41 ofthe servo-motoris'conveniently such that they opposefeach:other' in electrical effect and 4prevent rotation ofthe motor whenthere is `no voltage atthe` amplifier input rand consequentlyxno E.M. F. developed ,in the windingdl:

when the gaivanometer beam at is in itsj center or'nu`ll position (although-contacts Si) are v the motor will' ynot turn and there will beY no chan'ge of. the adjustment of the positionVl of the tap on the slide wire I3 6. Butif thebeam `39 ls'deected against the stationaryA contact 4i, ,a voltage will' be impressed (froml one-halfbf the secondary of transformer `43) upon theJnput lof the amplifier such asl Vto produce in the 'outputof thelatter an'E. M.I F.

f having a predetermined definite phase. relation to .'25l

the' voltage on the fleldcoil of the motor 48. Consequently, the effect of one set of shading coilswill I'be assisted and that ofthe other set will be opdirection of current in the coil.38, into contact with one or the other of the contacts 4i, 40; and throughv ,ins'trumentalities presently to be described, closure of the circuit through one or the other of these contactsis adapted'to initiate op-i eration of a servo-motor 42, forcorres'ponding adjustment, in one direction or the other, of the tap .position on vthe slide wire 36. Thus, if the potential generated between .the liquids in the cell E and the electrodes 1 and 2d upon Whichthey L respectively impinge, are equal in value, no cur- 'rent will flowvth'rough the coil 38 and itsbeam 39 will remain in center position, out of engagement with either of the contacts 4l and' 40. On the otherY hand, if a voltage difference exists between the.-electrodes ofthe cell, the beam will. be deflected to one side or .the other, and opera-` tion of the servo-motor will result, Vfor adjustment` of the position of the tap on the slide -wlre 36.

Although .other systemsmay be employed for `electrical control. of the variabley resistance 36, f by they galvanometer relay, a notably advantageous system is shown which in its fundamental -features embodies the motor control apparatus f v(including an amplifierv and'a shaded pole servo-- motor having wound shadingcoils energizable by the amplifier) of the type disclosed in the patent to John R. MacKay, No. 2,234,349, granted March 1'1, 1941, and also mBrii-,ish Patent No. 493,457-,

'Cof Wallace .-& 'I 'iernan Products Inc., for Motor 'control apparatus, dated December 29, 1938.

In the illustrated system, a supply transformer 5 3, having .its primary energized from the same A. C. llilrie M as for the transformer 33, is provided with a center tapped secondary. The end terminals of the secondary are connectedjto the respective' contacts 40, 4I, as shown, while the movable contact or beam' ofthe galvanometer a d the center tap of the transformer secondary, e

connected to the'inputterminals of an Aamplifier 45, say, an electron tube amplifier equivalent to the final stageof the `type of amplifier illustrated the opposite direction. To illustrate theioperation of the system, let` posed and overcome, so that the motor runs in one direction. Lilewise if the beamisdefiected against the contact' the .impressed voltage on the amplifier (derived from the other half of ,the

.secondary of transforment) win be such that the output voltage ifs in effectl80 opposite in phase to the voltage produced under they` conditions previously described; and the motor Will be driven in it be assumed that vthe liquid flowing inthe pipe free chlorine. Thepresence'vof-chlorine in the liquid will cause a voltage to bedeveloped at its junction With the eleCtIOde T, 0f the cell 5. If l't is further assumed that the, rtap on the'resistance 36 is in such position that no effective current is flowing throughthe chlorinegenerating cell 26, the portion of the s'ampling which reaches .the feed chamber 2l' and electrode 24 is'and remains completely de-chlorinated (by the'de-chiorinating device I2) so that no potential-due to chlorine .is developed at the junctionfof that liquid with theelectrode 2B.V The resulting difference of p0- tential between the electrodes 2e' and. l creates a.' flow of current through the'c'oil Stof the gale` vanometer relay, so as to deflect its beam against, say. the stationary contact 4|. Thereupon by virtue of the instrumentalities described hereinabove, the motor 42 is caused to rotate in a direci' tion to decrease the resistance of theslide'wire inthe cited MacKay patent or British patent.

JThe amplifier has an' output winding 46 which is connected `in series with the opposed sets of 36.. it being conveniently assumed that the connection of the motor to the pinion 5i and rack 52 or other suitable meansfor slide wire adjustment is suchthatthe :motor operation resulting from losure of contact 4i will move the sliding contact in such direction.

Current through the circuit of the cell 26 being thus established or increased above an ineffective' I has been treated to produce in it a residual of beam will return to the center position, interruptchlorine concentration in the main .body of liq-` uid decreases, a difference of potential, in the opposite direction, will be vestablished between the electrodes l and 24, whereuponthe motor 42 will be operated to reduce the current in the 'circuit of the generating cell 26, and the recorder will yield a correspondingly lower reading. And in similar fashion if the chlorine concentration in the sampled material rises, operation of the system in the other direction wll result (as previously described) and the recorder 35 will show a Proportionately higher reading.

In many cases, either upon initial operation of the system or upon subsequent change in the condition of the sampled liquid, there may be some delay before equilibrium is established between the solutions laving the `electrodes 1 and 2l. To prevent vor minimize hunting under such f circumstances, an intermittent Contact device may be included comprising the cam 49 having a high spot or projection 53 for periodically closing the, contacts 50 in the eld circuit of the motor 42.

vThe cam 49 may be rotated at a preferably constant rate by suitable means, such as a motor 54 energized from the A. C. line 44. It will now be understood ,by those skilled in the art that the control of the slide wire 36 can only take place during the intermittent periods when contacts 50 are closedpreferably short periods spaced by'relatively longer intervals-and that the, peripheral length of the cam projection 53 or the speed of the motor 54 or other suitable control may be so designed or adjusted as to provide both adesirable rapidity of response and a reduction of hunting tendencies to a convenient minimum. l

Fig. 1 also shows further apparatus whereby automatic control may be had, for instance, to maintain the chlorine concentration in the liquid in pipe at a desired value. Although any of a wide variety of reagent feed control 'devices may be controlled by systems of the type shown, a simple arrangement includes high-low contacts |55, |56 spring mounted on either side of the arm |51 of the galvanometer 35, in such position that when the arm departs above Orbelow a position or permissible range of desirable chlorine content in the liquid of pipe I, a central contacting element |58 engages .one or the other of the contacts |55, |56. Y.

As shown, the latter, and the central contact |58 through a current source |59, are connected to the terminals of an electrically operated control valve |60 for a chlorinator |6|; the valve |50 being conveniently such, as will now be understood by those skilled in the art, that establishment of the circuit through one or another of the high-low contacts respectively moves the valve to a more closed or more open position. It will be understood that the chlorinator |6| is adapted to feed chlorine into the liquid flowing in the pipe l at some point previous in the flow of the liquid to that part of the pipe shown, this arrangement being wholly conventional. Consequently., the now 'of chlorine from the feed. device IBI to the pipe l is reduced or increasmuas may be necessary to restore the residual chlorine ot the liquid to its desired value, whereupon the arm |51 resumes its normal position' in which, both contacts are open. `It will be understood that if the control system tends to hunt,- delay apparatus (not shown), e. g. similar to the cam 49 and contacts 50 previously described, may be associated in the circuit of valve |60.

' Figure 2 illustrates a system embodying certain modications or alternative devices, but also gen-` erally including 'a number of elements which are similar to those of Fig.'1, functioning in the same ,manner and Vbearing the same reference numbers, so that repeated description of them is unnecessary. In Fig; 2 a potentiometer recorder 55 has been shown in lieu 'of the galvanometer relay 31 of LFig. '1. tiometer recorders are now commercially 'available, an example being one known as the Micromax recorder which is manufactured by the Leeds & Northrup Company of Philadelphia, Pa.

This recorder ls of the so-called nul1type and draws no current from the cell 5 except momentarily when the potentiometer is adjusting itself to neutralize voltage changes which have taken place between the electrodes 'l and 24 of the cell 5. Furthermore, thepotentiometer is equipped with highlow*contacts 55a, 55h, which are arranged to be engaged or closed (in fashion generally similar to the contacts 4 |-4 of Fig. 1) whenever the indicator arm departs a given value from a predetermined control point-i. e., upon a predetermined small change in potential difference between the electrodes l and 24 of the cell 5.

In the system of Fig. 2 there is also shown a diierent form of apparatus for introducing chlorine to the dechlorinated liquid from the constant level box I6. Thus, in Fig. 2, there is diagrammatically illustrated a chlorine solution feeding device 56 which may be of any suitable kind, for instance of the general type described in myv U. S. Patent No. 1,593,109, issued July 20, 1926. It may be explained that the device 56 is adapted to feed a chlorine solution of known concentration through the pipe 56a, and thus into the cell feedingchamber 2| for mixture with the de-chlorinated water. The rate of feed of the device is conveniently governed by the rate of drive of its mechanical operating parts.

For control intermediate the potentiometer recorder and the solution feeding device ,56 in Fig. 2, a variable speed box and motor drive unit 51 may be provided, including a suitable driving motor (not specifically shown) which has a drive pulley 58 to operate a belt 59 which thus rotates the drive pulley of the feed device 56. As will be understood, the variable speed box 5l includes a continuously variable speed drive mechanism-or other apparatus which may be adjusted, for exmechanically connected to each of a pair of opposed motors 62, which have their respective field coils 53 and 64 connected to the high-low con-v tacts 55h, 55a of the potentiometer. The connection of the winding 63, 64, to and selectively through the contacts for energization by the A. C. line 55, is such that when the potentiometer arm is at its normal control position (representing no appreciable change in the potential difference across the cell 5) both the eld windings are disconnected from` the line 65, but when there is a Various types of suitable potensodass ing to the direction of such departura-soas to cause rotation of the speed control Wheel 6|- in of feed of chlorine'solution'by the device Blto th chamber 2|. 'I'hat `is to say; if there is a departure from chemical ,balance of the .liquids in the 'respective sides of the cell 5, a corresponding one of the potentiometer control contacts 56a, 55h will be engaged so as to increase'or decrease the rate of 'chlorine solution feed in such way as to restore .chemical balance. The chemical condition esconcentration) of the liquid in pipe I and is readily measurable by the speed of rotationiof the drive 56-'60 for the feeding device. Accordadily 'calibrated to indicate the chlorine concentration of tle liq- `uidin'\pipe|. 1

i It .will now be 'readily'understood that otherA devices than the tachometer may be. employed, to indicate or register the rate of operation of lthe feedingl device and thus the chemical condi- 30 tion of the sampled liquid; for example, a pointer or recorder pen arm .may be operated from the. control wheel 6I of the variable Speedbox-l'i, in such-way .that the angular or other position liquid in 'feeding tube 89 will'. dependv upon the .vertical position of the tube 1I, i. e., the dis- -tance oi' its lower end below the liquid level, the

space above -the liquid'in. the jchamber being a direction for increasing or decreasing the rate 5 'sealed from fthe outer atmosphere.I Accordingly, the oriilce I maybe arranged to feed chlorine solution into the fees. chamber ,uterine cen (see Figs. lf andZ, the sample .feed pipe I8 be ing connectedl tothe constant level box I6 inlo 'the manner of Fig. 2) and the readings. of the 4pointer 'Il von 'scale 'I5 may'thusbe correlatedto indicate the rate of chlorine addition through.

the orifice 1U, inasmuch as suchrate of addition Jvaries with the vertical'position of the assembly tablished by the feeding device is thus kept equiv- 15 alent to the chemical condition (es. the chlorine "II, 12,' 14. If desired, aj supplementary solution supply and constant level'device (not shown) i maybe' provided for the chamber B6, to prevent errors on the scale 'I6 due tochanges of levelv in the chamber. j

0 Thus, if the apparatus in Fig. 3 is substituted for the chlorine cell 26, galvanometer'recorder' 36 and associated control circuit of. Fig. l, the vremaining apparatus will' be operated in sub- Fstantially the same wayfand upon a diierence in Achlorine concentrations voi the/liquids in the two sides of the cell 5, the resultingpotential difference will cause operation of the'motor 42 and consequent adjustment of the chlorine solution feed' in such fashion as to restore chemical balance. v

Somewhat modiied forms of liquid feedingy devices are shown` in Figs. 4 and 5; these again being adapted to handle,.for examplefa chlorine .solution of known concentration, as in the Ycase assumed by such element will represent-the chiclof Fig. 3. In Fig. 4, the solution -is contained rine concentration.

In many cases, .certain elements' of thei'ecord ing potentiometer may be omitted, for instance the chart drive, ,pen armand chart ;l yet sometimes in an inverted ask or chamber T6. A u -tube 'I'I has one leg 'Ila extending up into the chamber-withits upper end opening above theliq= uid, the portion. ila also having a small openit mayI lie-desirable to keep such chart record, 40-ing 11b intothe liquid near the lower part of the which will indicate any errors in thereadings of 'f fthe indicator B6 that might result from vinability of the system to regalnbalance promptly after' f large uctuations in the composition of the liquid 4 Various other'.l types of adjustable feeding devices, such as calibrated .and readable orices; va1ves.or \the like, may *also be employed for( eiecting addition of the substanc'under test,

- to the liquid which' has been treated in 'the ae- 5" vice I2. For example, in Fig. 3 there is. shown yyet anotherJ form of chlorine solution feeding device which may be utilized instead of the feeder 56 in Fig. 2 and which may be readily `controlled by means, for instance, of an electrical system 55 `such asI that of Fig. 1, embodying the galvanometer relay 31 and the servo-motor d2.

Referring to Fig. 3, a sealed chamber 68-contains chlorine. solution of known concentration. An outlet tube 69, conveniently extending from 60 the chamber 68 ata point near the bottom thereof, terminates inv a ,downwardly directed orice 'I0 which is designed or calibrated so that it will pass a predetermined amount of solution for any given head of liquid impressed' upon it. A 65 tube 1I, having itsupper end open to the atmos- Dhere, extends down intothe liquid inthe cham; ber 66 and is arrangedto be'moved in avertical direction, say by the rack I2 and the'spurgear f 'I3 operated bythe motor 742.A -The adjustable 70 assembly, including the rack 12,' may-carry apointer 'I0-to traverse a scale 15.'

As the lower end of the tube -`II Ibelow the level of the liquid in- .thechamberyit will now flask. The'other leg 'I'Ic of the' U-tube is open to the atmosphere'and conveniently has a lower extension, such as shown;A for stabilizing the feed of solution and to provide 'an outlet for such 5 feedas hereinafter explained.. It will `now be understood that, the solution' is maintained ata substantially constant level in the lg 'IIc vof the Utube, regardless of the 'actual level of the liquid inthe flask 16. That is to say, as the liquid tends to rise/above such predetermined level in the leg "I'Ic, the reduced pressure above the liq uid inthe flask tends to prevent such rise; while 1 upon withdrawal of liquid from the leg Tlc, air

may be sucked backI in through. the 'U-tube so as to permit rise' of the'liquidin the leg 11e to the predetermined level from which it may have f of the lower or discharge end of the tubebelow the 4assembly comprising the yiiask 16 and the U-tube Ti. Inasmuchas the flow. through the capillary tube may depend to aI certain extent on'the temperature of 'the liquid, the lower portion of the U-tube` l1, and its leg y'I'Ic, are conveniently enclosed in a chamber 18, through which cooling liquid may pass, to maintain a be appreciated that the head or pressure on the- 75 .constant temperat'ure'forthe supplied solution.

' y not only desirable for the usual purposes of con- Relative adjustment is provided between the lower end of the tube 'IS- 8U and the assembly constituting the 'flask 16 and U-tube 11, so astq adiust vthe rate of solution feed. Thus the last'- erations than the detection of chlorine, such for yinstance as in the measurementof acidity or alkalinity or other condition in a flowing material, which is susceptible of neutralization (or mentioned assembly may be vertically displaced iv elimination), measured re-establishment, and

by a rackV |12 and pinion |13, the pinion being driven by suitable apparatus, such as the vservomotor 42 (not shown in this figure) as illustrated and describedin connection with Figs. 1 and-3.

The vertical position of the assembly will cor- 10 respond to the rate of feed of chlorine solution and may be calibrated accordingly; and it will be understood that this simple form of apparatus is sometimes preferred, inasmuch as the calibration of the vertical position in terms of 15 chlorine feed is substantially` unaffected by the' quantity of solution in the supply chamber` and there is no need for a constant level device in the chamber.

Fig. 5 illustrates a modification of the appa- 20 Ultube 11 and associated adjusting apparatus, 25

the withdrawal of liquid from the open leg 11o is achieved through a calibratedloriflce 82 in the bottom of` the leg 11e, opening into a tube-*19a which may discharge into the chamber ,2| by a flexible-connection (not shown) disposed -simi- 3 l larly to the tube 8U of Fig. 4. The adjustment vvof solution feed ismade .in the same manner.

as in Fig. 4, and the rate of such feed for any 'subsequent' detection. f

'In' accordance with the (provisions of the patent f statutes,`I have herein described the principle of operation of my invention, 'together with the ap- A paratus which are now considered to represent the .best embodiments thereof, but I- desire to have it understood that the apparatus disclosed is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and others omitted and some of the features of each modification may be embodied in the others without interfering with the more general results outlined, and the invengiven vertical position of the movable assembly .e stream of the untreated fluid to determine the is determined by the ,size of the prince s2.

Although the invention may be applied `to con` trol Purposes instead of or in addition` to direct measurement (for example, by operating contacts or other devices from the recorder of Fig. 1'V as disclosed above, or from the tachometer 66 oi' Fig. 2, to control a chlorinator for pipe l;` or even by operating the chlorine feed to the sample line at a constant desired rate and causing chemical unbalance to adjust the main chlorinator to restore balance), the systems are of notable utility for the measurement or recording of the chemical condition of the material tested. For example, such registration of chlorine content is inaccuracy as may occur in the cells or the like used for testing. Moreover, in testing chlorinated liquids, it is often desirable to sample at some distance from the point of chlorination, i. e.at a point where the then residual content of chlorine affords the best indication that the intro- ,65

duced chlorine has been and is serving its intended purpose. Thus the `present invention, which requires sampling at only that one point and no sampling of the unchlorinated liquid,

avoids the inconvenience and other dilculties of one or more long sampling lines which would-be needed for a comparison of samples taken from remotely separatedplaces.

`It will now be appreciated thatfprocedure of relative concentrations of said chemical constituent in said streams, and detecting differences in i the concentrations of said constituent Vof the compared streams.

2. The method of maintaining a predetermined content of a substance in a fluid, which comprises continuously subjecting a portion of the fluid flowing as a stream at constant velocity to treatment for removal of the substance as such therefrom, continuously adding a fresh quantity of the substance to the said treated portion at an adjustable rate, continuously comparing said treated portion with an untreated portion of the original fluid to detect any actual difference in their respective contents of the substance, varying said rate until said actual differences become zero, and controlling the concentration of said substance initially in said liquid to bring the concentration thereof determined as aforesaid to a predetermined value according as the adjusted rate of addition of said substance aforesaid diii'ers from said predetermined value.

3. The method of claim 2, for detecting changes inthe concentration of a substance which is adapted to produce a detectable electrical effect at'an electrode exposed to the fluid containing said substance, wherein the comparing step is effected by exposing the rst mentioned fluid portion, after the fresh quantity of said substance has been added thereto, to an electrode, exposing said untreated portion to another electrode, and detecting the difference in electrical effects respectively produced on said electrodes as representative of differences in the concentrations of said substance in the portions thus compared.

4. The method 'ofdetermining the chlorine content of a liquid, which comprises continuously dechlorinating a portion of the liquid flowing as a continuous stream at a constant velocity, adding chlorine to said portion at a determinable adthe character described is applicable to other opinstable rate, continuously comparing Said D01'- detecting the difference in Y'theirconce'ntrations 5 chlorine to the'ffirst vportion in correspondencc ler'lce of chlorine content ofl the'`cbmllaredpor continuous stream at a constant velocity to de-l J dechlorinated and rechlorinated portion andthat` dechlorinatedportion so as tolreduce said poi" I ing continuously as a stream at constant velocity,

. continuouslyadding chlorine to said portion at.'

-ing stream of the liquid `of the same chlorine con- 35 and a' constant flow regulatingmeans, a second' e duit means,'means for supplying said constituent said supply means to produce a zero diil'erence esta tionwith an untreated portion 'ofthe lilliuidiY said bodyra first'conduit means for one of said' streams, connected to said cell apparatus, said conduit means including a chamber constructed v .to contain-means-ior removing available chlorine 5 as such and to contact said iirst stream with said of chlorine. adjusting the rate of,;addition of with the detected difference to produce equivations and'thus to reduce vsuch ditierenceitozera and determining the adjusted rate of chlorinefadl dition as directly yindicative of the chlorinecontent of the liquid.

5. The method of detectingthe chlorine 4'content of a liquid, which comprises continuouslyf l said rst conduit `means andcon-nected thereto subjecting .a portion of the liquid flowing as aintermediate said chamber and said-cell apparatus, the las't named means including electrolytic chlorination treatment, .continuously addingll.chlorine-generating means constructed and archlorine to said dechlorinated'portion at a Avari f able rate, continuously detecting and converting- Y ldirectly ,depending upon th` current passing Ysecond conduit means for the other of said streams connected tosaid cell apparatus and bysaid' ilrst .conduit means, meansxfor supplying diierence between the chlorine conteiit of/said therethrough, and means-connecting said cell ap- A l paratus and said means for supplying chlorine of an untreated portion vof the liquid into 'a di'f- 20` responsive to changes -in the lrelative `concentrations of available chlorine in the two streams in' ference of electrical 'potentiaL- adjustably varying vthe rate of'addition of chlorine added to said said cell apparatus and arranged to regulate'the tential diierence to. zero, and detecting .tlfeadjusted rate of addition of rchlorine necessary to reduce the potential difference to zero asrindicative of the chlorine content of the liquid which is to'be detected. I

6 In a method f detecting changes in the chlorine concentration of a liquid, the steps com- .prising dechloririatinga portion 'of the liquidLilow- -trolytic means to supply chlorine to said' ilrst 25 stream in accordance with such changes.

concentration of a given constituent in a body of 'paratus so constructed as to contain and compare 30 ,the concentrations of said constituent in two con- Ltinuously ilowing sample streams from s' id body, "said electrochemical cell apparatus eo prising 'a a known rate, takingr a second continuouslyiiow- Jporous diaphragm and having an electrode in tent as the main body ofthe said liquid, and continuously comparing by measurement the relativd `chlorine Icontents of the two said streamsI 7. In apparatus for detecting changes in the concentrations fa given constituent in a, body or' liquid, in combination, 'electrochemical cell apparatus so constructed as to contain and compare the concentrations of said constituent in tw'o continuously iiowingfsample streamsfrom said 4 bodyy a rst conduit. means 4for one o! said streams, connected nto said cell apparatus, said conduit means including a chamber constructed to contain means for removing said constituent as such and to contact suchstream with said means,l

means, and a` constant flow regulating means, a second conduit means for the otherr of said said 'el'ectrochemical cell apparatus and by-passing the abovestated elements included in said rst conduit means; means for supplying said constituent connected to said first conduit means intermediate said chamber arid said electrochemi- 0 cal` cell apparatus and electrical'means connecting said electrodes of said electrochemical cell lapparatusand the means for supplying said constituent responsive to changes in the potential be# f tween` said electrodes and in turn responsive to the changes of the relative concentrations of said constituent in said two streams and arranged to regulate said supply means in accordance. with such changes.

10. In apparatus for detecting changesin the concentration of a given constituent in a body of conduit means for the other'of said streams connected tosalidfcell apparatus and ley-passing the above stated elements included insaid first conconnected to said first. conduit means `'inter- 55 mediate said chamber andesaid cell apparatus, and means connected tol said cell apparatus and said means for supplying said constituent responsive to changes in the relative concentrations of said constituent in said two strea-ms in said cell ,60 apparatus and arranged 'to regulate said supply means in accordance with such'changes so as tct vconstructed asto contain and compare the conchange the rate of Vsupply of said constituent by centrations of said constituent vin two continuously ilowing sample' streams .from said body, a lrstfconduit means for one of said streams, connected to said yanalytical apparatus, said conduit means includinga chamber constructed to contain'means for. removing said constituent 'as such and to contact said stream with said means, and a constant flow regulating means, a second conduit means, for the other df said streams con'- nected to said analytical apparatus and bypassing the above stated elements included in between the concentrations oi said constituent l in said two streams, whereby the adjusted rate of supply of said constituent by said supply means is directly indicative of the concentration of said constituent in said body of liquid.

8. Apparatus for detecting changes in the concentration of lavailable chlorine in a body ci' an aqueous liquid, in combination, electrochemical cell apparatus so constructed as to-,contain and compare the concentrations of available chlorine in two continuously ilowing 'sample streams from constituent connected to said first conduit means Vmeansand a ,constantl iiow regulating means, a

1'0" passing `vthe above stated elements included in' available chlorine to the stream owing ,thro.`ugh

ranged to supplyll'chlorine at a'variable rate,

' rate atl-which current-.passes through said elec- 9. In apparatus 'for vdetecting changes in the liquid, incombination, electrochemical cell p-Q cell having two compartments separated by 'a' f each of said. compartments arranged'for contact e withliquid therein,` a iirst conduit means for one as such and to contact s aid stream witi said '5 streams connected to the `other compartment of liquid, in combination, analytical apparatus so- 75 said lilrst conduit means, means for supplying said ,intermediate said chamber and saidanalytical apparatus, and means connecting .said'analytical apparatus and said means for supplying said con- Y stituent responsive to changes in theF relative conchanges.

11. In apparatus for detecting changes in the concentration of a given constituent in a body of liquid, in combination, electrochemical'cell apparatus so constructed as to contain and com- -pare the concentrations o f said constituent in two included in said first conduit means, means for supplying said constituent connected to said mixing chamber, and means connecting said cell ap- Y paratus and said means for supplying said ccncontinuously flowing sample streams from said 'v'body, a first conduit means for one of said streams, connected to said-cell apparatus, said conduit means including a chamber constructed to contain means for removing said constituent l as such and to contact said stream with said second conduit means for the other of said streams connected to' said cell apparatus andk bypassing the above stated elements included in said ilrst conduit means', means for supplying said K constituent, connected.v to said ilrst conduit Y means' intermediate said chamber and said cell apparatus, and means connecting said cell ap-k liquid, in combination, 'analytical apparatus so,

constructed as to contain and compare the concentrations of said constituent in two continu.- ously flowing sample streams from said body, a first conduit means for one of said streams, connected to said analytical apparatus, said conduit means including a chamber constructed' to contain means for removing said constituent as such andto contact said stream with said means, a mixing chamber, and a constant ow regulating means, a second conduit means for the other of said streams connected t'o said analytical appara@ tus and including constant ilow regulating means and by-passing the above stated elements included in said first conduit means, means 4for supplying said constituent connected to said mixing chambenfand means connecting said analytical apparatus and said means for supplying said constituent responsive to changes in the relative concentrations of the constituent in the two streams in said analytical apparatus and arranged to regulate saidsupply means in accordance with such changes.

13. In apparatus for detecting changes in the concentration-of a given constituent in a body of liquid, in combination, electrochemical cellapparatus so constructed as to contain and compare the concentrations of said constituent in two continuously flowing sample streams from said body, a first conduit` means for one of said streams, connected'to said cell apparatus, said' conduit means including a chamber constructed to contain means for removing said constituent as such and toA contact said stream with ,said

means, a mixing chamber, and a constant vilow 'stituent responsive to changes in the relative concentration of the constituent in the two streams inthe cell apparatusand arranged to regulate Asaid supply means in accordance with such changes.

14. Apparatus for detecting changes in the concentration of a ,given constituent ina body of liquid.. in combination, electrochemical cell apparatus so constructed as to contain and compare the concentrations of said constituent in two continuouslyf'ilowing sample streams, from said'body, a ilrst conduit means forpne of said streams, connected to said cell apparatus, said conduit means including a chamber constructed to contain means for removing said constituent as such and to contact said stream with said means. and a constant ow regulating means, a second conduit means for the other of said streams connected to said cell apparatus and by-passing the above stated elements included in said rst conduit means, a container for a solution of said constituent in a liquid which is the same as the iirst named liquid, means for supplying said solution from said container at a variable rate and connected to said iirst conduit means inteimediate said chamber and said cell apparatus, and means connecting said cell apparatus'and said means for supplying. said constituent responsive to changes in the relative concentrations of said constituent in the two streams in said cell apparatus and arranged to regulate the rate of supply of said solution in accordance with such changes.

15. In a method of controlling the content of a given chemical constituent in a main body oi material, continuously treating a portion of said material ilowing as a stream at a constant velocity, to remove said constituent, thereafter continuously subjecting said portion to treatment of variableand determ'inable extent for reestablishment of a content of the constituent which is equivalent to that of the main body of material,

' continuously comparing by measurement the con- .re-establishment treatment to maintain equivalence of said portions with respect to said chemical constituent, subjecting the main body of material to a treatment adapted to modify its content ofsaid constituent, and converting departure of the re-establishment treatment from a predeternined value thereof into variation of the treatment of the main body to maintain its vcontent o'i the constituent at a predetermined value.

16. In a method of detecting the content of a given chemical constituent in a material, continuously treatinga portion of said material flowing as a continuous stream at a constant velocity to remove said constituent, continuously subjecting said portion to treatment at a variable rate for reintroducing said chemical constituent, to establish equivalence of content of the constituent in said/treated portion and in the untreated material, correlating said rate with the content of the constituent in the untreated material so that both the rst named portion and said untreated material 'have the same concentration of said constituent, and translating departure of said rate oi treatmentfrom a predetermined value into an indication of departure of the content of the chemical cell apparatus so constructed as to contain and compare the concentrations of said constituent in two continuously owing sample streams from said body, a first conduit means Afor one of said streams, connected to said cell apparatus, said conduit means including a chamber constructed to contain means for removing said constituent as such and to contact said stream with said means, and a constant ilow regulating means, a second conduit means forthe other of said streams connected to said cell apparatus and by-passing the above stated elements in said ilrst conduit means, means for supplying said constituent connected to said first conduit means intermediate said chamber and said cell apparatus,

means connecting said cell apparatus and said means for supplying said constituent responsive to changes in the relative concentrations of said constituent in the two streams in said cell ap paratus and arranged to regulate said supply means in a direction such as to bring the concentrations of said constituent in said two streams into exact equality, and means responsive to the adjusted rate of supply of said constituent by said supply means for regulating the amount of said constituent in the liquid in said main.

to contain means for removing the chlorine as such and to contact said vstream with 18. In apparatus formaintaining the concentration of available lchlorine in -a body of an aqueous liquid flowing in a main, in combination,.

electrochemical cell apparatus so constructed as to contain and compare two continuously flowing sample streams from said body, said cell apparatus comprising a two-compartment potential cell wherein said compartments are divided by a porous diaphragm and wherein there is an electrode in each of said compartments, a rst conduit means for one of said streams, connected said means, and a constant flow regulating means, a second conduit means for the other of said streams connected to the other compartment of said cell apparatus and bi1-passing the above stated elements included in said iirstl conduit means, anele'ctrolyticy cell for supplying chlorine at a variable rate in proportion to the amount of current passing therethrough and connectd to supply chlorine to the stream in saidrst conduit means intermediate said chamber and said cell apparatus, electrical circuit means' including the electrodes of said cell apparatus and connected to control the amount of current passing through,

said electrolytic cell to bring the concentrations of available chlorine in said two streams in said cell apparatus to exact equality, means responsive to the amount o! current supplied to said electrolytic cell for controlling the amount of chlorine supplied to the liquid iiowing through said main, and means for indicating the adjusted amount of current passing through said electrolytic cell for thereby indicating the concentration of available chlorine passing through that portion of the main from which said nrststreamis drawn.

19. The method of determining the concentration of a chemical in a body of liquid which comprises flowing two sample streams from said liquid body, removing from one stream said in known quantity, determining the difference in concentrations of the` chemical in the two streams after the addition'of the chemical to the one stream and varying the rate ofaddition of quired to maintainl the concentration of the to one compartment of said cell apparatuasaid conduit means including a chamber constructed vmeasure or the concentration of chemical in the two streams the same being a the chemical in saidbodyof liquid. w l

I CHARLES F. WALLACE.

available v 

